Project: Lake Mead Intake Hydraulic Tunnel
Customer: Vegas Tunnel Constructors
The Ballard Tunnel Support Division supported the Lake Mead Intake Number 3 project. This was a unique project due to the extraordinary pressures at the tunnel boring machine (TBM) head. Pressure was anticipated to reach 14.5 bar and all equipment was to be constructed with a design working pressure of 17 bar. The extreme pressures, and in fact the highest in the world to date, required a type of support that is becoming more popular. Saturation, or SAT was brought into play. This was one of the first projects in the world that was prepared fully for SAT operations.
Compressed air workers, saturation divers, man lock tenders, medics and other specialized labor and consultants are provided by the Ballard team. We provided job specific hyperbaric manual to assist with OSHA variances and performed the saturation system commissioning and integration of the TBM system.
The project purpose was to build a potable water intake tunnel into the base of Lake Mead, the vast reservoir created by the famous Hoover Dam on the Colorado River near Las Vegas, Nevada. The logistics of the project demand that the TBM be a hard rock machine that would be able to convert rapidly from an open-faced faced system to a closed pressurized system capable of withstanding potential hydrostatic pressures up to 17 bar maximum. Currently water is drawn from two existing intake structures located on Saddle Island. Critical drought conditions over past seven years have lowered the surface of the lake to critical levels. If the water level continues to decline, existing Intake No. 1 will become unusable. A drop in lake level to elevation 305m (1001ft) would render the previous intake unusable.